In a typical refrigeration system, a refrigerant fluid such as R-12, R-134a or other freon type refrigerant, is compressed, expanded to generate refrigeration, and then warmed whereby refrigeration is passed from the refrigerant to a refrigeration receiver. The warmed refrigerant is then returned to the compressor and the refrigeration cycle repeats.
The compressor used in the refrigeration cycle is typically oil lubricated and some of this lubricant leaves the compressor with the compressed refrigerant. It is generally good practice to use a lubricating oil, such as a polyolester-based oil, which is highly soluble with the refrigerant. In this way substantially all of the lubricating oil which leaves the compressor with the compressed refrigerant is returned to the compressor with the recycled warmed refrigerant. If a significant amount of the lubricating oil which left the compressor were to remain in the refrigeration circuit and not be returned to the compressor, there may be inadequate lubricating oil in the compressor causing loss of compressor efficiency and perhaps even leading to compressor failure.
Very low temperature or cryogenic refrigeration is becoming increasingly important, such as for use in such fields as energy generation, energy transmission and electronics. Any improvement in refrigeration systems which would enhance the ability to generate and provide refrigeration at a cryogenic temperature would be very desirable.
Accordingly, it is an object of this invention to provide an improved system for generating and providing refrigeration at a cryogenic temperature.